/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You under the Apache License, Version 2.0
 * (the "License"); you may not use this file except in compliance with
 * the License.  You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.apache.flink.streaming.api.functions.aggregation;

import org.apache.flink.annotation.Internal;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.typeinfo.TypeInformation;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.api.java.tuple.Tuple;
import org.apache.flink.api.java.typeutils.TupleTypeInfo;
import org.apache.flink.streaming.util.typeutils.FieldAccessor;
import org.apache.flink.streaming.util.typeutils.FieldAccessorFactory;

/** An {@link AggregationFunction} that sums up fields. */
@Internal
public class SumAggregator<T> extends AggregationFunction<T> {

    private static final long serialVersionUID = 1L;

    private final FieldAccessor<T, Object> fieldAccessor;
    private final SumFunction adder;
    private final TypeSerializer<T> serializer;
    private final boolean isTuple;

    public SumAggregator(int pos, TypeInformation<T> typeInfo, ExecutionConfig config) {
        fieldAccessor = FieldAccessorFactory.getAccessor(typeInfo, pos, config);
        adder = SumFunction.getForClass(fieldAccessor.getFieldType().getTypeClass());
        if (typeInfo instanceof TupleTypeInfo) {
            isTuple = true;
            serializer = null;
        } else {
            isTuple = false;
            this.serializer = typeInfo.createSerializer(config);
        }
    }

    public SumAggregator(String field, TypeInformation<T> typeInfo, ExecutionConfig config) {
        fieldAccessor = FieldAccessorFactory.getAccessor(typeInfo, field, config);
        adder = SumFunction.getForClass(fieldAccessor.getFieldType().getTypeClass());
        if (typeInfo instanceof TupleTypeInfo) {
            isTuple = true;
            serializer = null;
        } else {
            isTuple = false;
            this.serializer = typeInfo.createSerializer(config);
        }
    }

    @Override
    @SuppressWarnings("unchecked")
    public T reduce(T value1, T value2) throws Exception {
        if (isTuple) {
            Tuple result = ((Tuple) value1).copy();
            return fieldAccessor.set(
                    (T) result, adder.add(fieldAccessor.get(value1), fieldAccessor.get(value2)));
        } else {
            T result = serializer.copy(value1);
            return fieldAccessor.set(
                    result, adder.add(fieldAccessor.get(value1), fieldAccessor.get(value2)));
        }
    }
}
